[llvm-bugs] [Bug 52142] New: [AArch64] 64-bit rev16 patterns are not recognized

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=52142

            Bug ID: 52142
           Summary: [AArch64] 64-bit rev16 patterns are not recognized
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Keywords: beginner
          Severity: enhancement
          Priority: P
         Component: Backend: AArch64
          Assignee: unassignedbugs at nondot.org
          Reporter: pavel.iliin at arm.com
                CC: arnaud.degrandmaison at arm.com,
                    llvm-bugs at lists.llvm.org, smithp352 at googlemail.com,
                    Ties.Stuij at arm.com

For the following patterns:
unsigned int
rev16_32a (unsigned int a)
{
  return (((unsigned int)(a) & (unsigned int)0xff00ff00UL) >> 8)
         | (((unsigned int)(a) & (unsigned int)0x00ff00ffUL) << 8);
}

unsigned int
rev16_32b (unsigned int a)
{
  return (((unsigned int)(a) & (unsigned int)0xa00ff00ffUL) << 8)
         | (((unsigned int)(a) & (unsigned int)0xff00ff00UL) >> 8);
}

unsigned long long
rev16_64a (unsigned long long a)
{
  return (((unsigned long long)(a) 
          & (unsigned long long)0xff00ff00ff00ff00UL) >> 8)
         | (((unsigned long long)(a) 
                    & (unsigned long long)0x00ff00ff00ff00ffUL) << 8);
}

unsigned long long
rev16_64b (unsigned long long a)
{
  return (((unsigned long long)(a) 
          & (unsigned long long)0x00ff00ff00ff00ffUL) << 8)
         | (((unsigned long long)(a)
                   & (unsigned long long)0xff00ff00ff00ff00UL) >> 8);
}
aarch64 clang -O2 generates:
rev16_32a(unsigned int):                          // @rev16_32a(unsigned int)
        rev16   w0, w0
        ret
rev16_32b(unsigned int):                          // @rev16_32b(unsigned int)
        rev16   w0, w0
        ret
rev16_64a(unsigned long long):                          // @rev16_64a(unsigned
long long)
        lsr     x8, x0, #8
        lsl     x9, x0, #8
        and     x8, x8, #0xff00ff00ff00ff
        and     x9, x9, #0xff00ff00ff00ff00
        orr     x0, x8, x9
        ret
rev16_64b(unsigned long long):                          // @rev16_64b(unsigned
long long)
        lsl     x8, x0, #8
        lsr     x9, x0, #8
        and     x8, x8, #0xff00ff00ff00ff00
        and     x9, x9, #0xff00ff00ff00ff
        orr     x0, x8, x9
        ret
The 32-bit forms of rev16 are recognised, but the 64-bit forms could also map
down to rev16 on X-regs.

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